** Next:** Formulae for Constant Angular
**Up:** Circular Motion and the
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**Definition:** Angular Velocity

**Angular velocity** of a rigid body is the rate of
change of
its angular position. Thus, if
= at *t* = *t*_{1} , and
= at *t* = *t*_{2} , then the **average angular
velocity** of
the body over the time interval
*t* = *t*_{2} - *t*_{1} is:

= = . | (4) |

= . | (5) |

**Definition:** Angular Acceleration

**Angular Acceleration** is the rate of change of angular
velocity with time. The
**average angular acceleration** of a rigid body over a time
interval
*t* = *t*_{2} - *t*_{1} is:

= = . | (6) |

= . | (7) |

10/9/1997